Abstract In water conservancy projects, the service life of finished engineering products is often determined by conditional factors such as water load and temperature changes. After completion, they are often operated with disease and many aging problems may occur. , which will lead to various accidents over time, which will not only bring a lot of trouble to inspection and maintenance, but also bring economic losses. Therefore, hydraulic structures must be inspected regularly and carefully, and both construction and design must be carried out in the early stage. Detailed consideration is the only way to ensure its safe operation. This article elaborates on the construction technology of reinforced concrete in water conservancy projects and is for reference only.
Keywords water conservancy construction; steel bars; concrete
1. Construction technology of steel bars in reinforced concrete construction
1. The steel bars entering the site must have a product factory certificate , if the product does not have a factory certificate or the procedures do not meet the requirements, or the material certificate does not match, or the batch size is unclear, it shall not be accepted and used. Rebar processing and installation engineering construction are also indispensable and important tasks in construction projects.
2. Connection of steel bars: The connection of steel bars can be divided into lashing, mechanical connection or welding. The stress conditions of steel bars at different locations are also different. Therefore, different connection methods should be used at each location based on the stress conditions, construction difficulty, economic benefits, etc. Using welding can save steel, improve the stress-bearing capacity of the structure, improve efficiency, and reduce costs. After the steel bar welding is completed, the appearance of the welded joints should be inspected in time. Joints that fail the appearance inspection should be cut out and re-welded. For axial tension and small eccentric tension members, the steel bars must be welded and tied and overlapped joints are not allowed. Before tying steel bars, carefully familiarize yourself with the drawings and check whether there are any discrepancies between the ingredient list and the drawings and designs.
3. Installation of steel bars: The installation of steel bars can be done in two ways: bulk and complete. The so-called bulk packaging is to transport the processed and formed single steel bars to the work surface. Binding or welding according to the drawing. The so-called assembly is to transport the processed steel frame on the ground to the work for construction and installation. Since bulk packaging has relatively low transportation requirements, it is widely used in small and medium-sized projects. Remind each other at any time during installation operations that the joints should be staggered and tied.
2. Formwork construction technology in reinforced concrete construction
The engineering technology of formwork in projects is constantly developing rapidly, and the development of reinforced concrete engineering has promoted the further improvement of the industrialization of building construction. Various formwork systems have developed rapidly. Especially in recent years, many scientific and technological achievements related to formwork have emerged. This not only speeds up the construction progress, but also plays an important role in ensuring construction quality and improving efficiency.
1. The production and installation of formwork must ensure that quality requirements are met. The formwork and its supports must have sufficient strength, stiffness and stability, and the support part must have sufficient support area. If it is assembled on the base soil, the base soil must be solid and a supporting plate must be added; the joints of the formwork should not leak grout. If there are embedded parts, they should be assembled firmly and the position must be correct; during rainy season construction, drainage measures must be taken; before pouring concrete, the soil and debris in the formwork must be cleaned up; the position and cross-sectional size must meet the design requirements
2. The order and method of removing the formwork should comply with the provisions of the construction organization design plan. The strength of the concrete when the formwork is removed should keep its surface and edges from being damaged. When dismantling, according to the situation, several suitable positions at the bottom of the formwork can be selected to reinforce with small steel parts and set up pry holes, which will facilitate the use of crowbars and will not damage the formwork and concrete due to the use of crowbars. And prevent large pieces of formwork from falling, and use special tools to reduce damage to concrete and formwork. After the formwork is removed, the board surface should be cleaned in time and an isolation agent should be applied to prevent dust from adhering to it.
3. Regulations and data requirements for formwork. The formwork has sufficient strength, stiffness and stability, can reliably withstand the specified construction loads, and ensures that the deformation is within the allowable range. The formwork surface requirements Smooth, smooth, tight seams, no leakage. The selection should be compatible with the concrete structure and characteristics, construction conditions and pouring methods. Formwork with a large structural surface requires the use of large formwork, and the material of the formwork bracket should be steel.
Both the vertical formwork and the inclination formwork must be equipped with sufficient internal supports and external railings to ensure the stability of the formwork. The support piles should be firmly fixed in two perpendicular directions.
3. Key points of construction technology of reinforced concrete
Construction technology of concrete in engineering Concrete is a building material widely used in civil and construction projects. Steel bars and concrete work together to improve the tensile strength and durability of the components, as well as their integrity and plasticity. The cement transported to the construction site should also have a factory certificate and quality test report from the manufacturer, just like steel bars. The user unit should conduct acceptance inspection and re-inspection if necessary. And they cannot be mixed to avoid errors.
1. Various raw materials of concrete should be inspected and qualified before they can be used. The meter of the concrete mixing plant must be accurate and can only be weighed after a zero point check and a warehouse opening certificate can be obtained. Concrete pouring.
2. During the concrete pouring and construction process, first of all, attention should be paid to the control of the interval time of concrete pouring, and the interval time should not be changed at will; secondly, attention should be paid to the retention of concrete construction joints. The retention of construction joints will affect the integrity of the concrete and lead to a reduction in the strength of the concrete. Therefore, the construction joints have become the weak links of the concrete structure; then, attention should be paid to the pouring of concrete at the construction joints. When pouring concrete at the construction joints, acceptance must be carried out according to the "Construction Quality Acceptance Code for Concrete Structure Engineering".
3. Concrete curing After the concrete is poured, effective curing measures should be taken in time to strictly prevent dehydration and shrinkage cracks. For concrete pouring in different situations and seasons, the following measures should be taken: The maintenance measures are also different. In short, as a curing agent, you should choose a product with a surface coating film that can fall off on its own. When choosing plastic film for maintenance, it should be sealed to prevent wind from blowing or falling off.
IV. Preventive and treatment measures for concrete cracks in water conservancy projects
There are many reasons for concrete cracking, including design, material, construction, external environment, etc. , the most common ones are plastic cracks, dry shrinkage cracks and temperature cracks.
1. First of all, plastic cracks can be prevented and cured by construction methods such as secondary plastering and timely maintenance. In addition, engineering fibers can be added (such as cellulose fiber, polypropylene fiber, glass fiber, etc.).
2. Then there is the problem of dry shrinkage cracks, which is more difficult. In terms of construction, the length of a construction section can be reduced to avoid cracking and the curing time can be extended at the same time. From the perspective of the concrete mix ratio, the amount of cementitious materials can be reduced while ensuring the performance of the concrete. Engineering fibers can also be added to improve the crack resistance of the concrete itself, and expansion agents can also be used.
3. Temperature cracks mainly occur in large-volume concrete projects. The problem is also more difficult and the methods are more complicated. 1) Reduce the heat of hydration; 2) Reduce the initial temperature of the material; 3) Improve the crack resistance of the concrete itself; 4) Increase the heat dissipation inside the concrete (arrange cooling water pipes); 5) Pay attention to thermal insulation on the surface of the concrete (reduce the temperature difference between the inside and outside of the concrete) .
V. Conclusion
It can be seen that the technical management and professional technical content within the construction enterprise are very important to water conservancy projects, because construction technology In the entire hydraulic construction, the quality and grade of the project are determined, and reinforced concrete is the most basic construction technology in the entire project, which must be strictly controlled. Therefore, it must be strictly implemented during the entire construction process. Systems in each link ensure the progress and quality of the project.
References
[1] Li Cuiqing, Yan Chaojun, Zhao Jiandong. Hydraulic reinforced concrete structures [M]. China Water Conservancy and Hydropower Press, 2009 07
[ 2] Ding Dajun. Modern Concrete Structure[M]. Beijing: China Construction Industry Press, 2000.